U.S. patent application number 10/090158 was filed with the patent office on 2002-10-10 for antenna apparatus.
This patent application is currently assigned to Murata Manufacturing Co., Ltd.. Invention is credited to Ishihara, Takashi, Kawahata, Kazunari, Miyata, Akira, Nagumo, Shoji, Onaka, Kengo, Sato, Jin.
Application Number | 20020145569 10/090158 |
Document ID | / |
Family ID | 18963076 |
Filed Date | 2002-10-10 |
United States Patent
Application |
20020145569 |
Kind Code |
A1 |
Onaka, Kengo ; et
al. |
October 10, 2002 |
Antenna apparatus
Abstract
An antenna apparatus includes a dielectric base, and a plurality
of feeding-radiating elements having different resonance
frequencies, each including a feeding electrode and a radiating
electrode which are disposed on surfaces of the base. A stub with a
common feeding point is disposed on a mounting substrate which
supports the base. The feeding electrodes of the feeding-radiating
elements are connected to matching points of the stub, thereby
achieving impedance matching for each of the feeding-radiating
elements.
Inventors: |
Onaka, Kengo; (Yokohama-shi,
JP) ; Nagumo, Shoji; (Kawasaki-shi, JP) ;
Ishihara, Takashi; (Tokyo-to, JP) ; Sato, Jin;
(Sagamihara-shi, JP) ; Miyata, Akira;
(Yokohama-shi, JP) ; Kawahata, Kazunari;
(Tokyo-to, JP) |
Correspondence
Address: |
Keating & Bennett LLP
Suite 312
10400 Eaton Place
Fairfax
VA
22030
US
|
Assignee: |
Murata Manufacturing Co.,
Ltd.
Nagaokakyo-shi
JP
|
Family ID: |
18963076 |
Appl. No.: |
10/090158 |
Filed: |
March 5, 2002 |
Current U.S.
Class: |
343/702 ;
343/700MS |
Current CPC
Class: |
H01Q 1/38 20130101; H01Q
1/243 20130101; H01Q 1/2283 20130101 |
Class at
Publication: |
343/702 ;
343/700.0MS |
International
Class: |
H01Q 001/24; H01Q
001/38 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 10, 2001 |
JP |
2001-111482 |
Claims
What is claimed is:
1. An antenna apparatus comprising: a base; a plurality of
feeding-radiating elements each including a feeding electrode and a
radiating electrode which are disposed on the base; and a substrate
arranged to support the base; wherein a common feeding point for
feeding a current to the plurality of feeding-radiating elements is
located on the substrate; a stub continuously expanding from the
common feeding point is disposed on a surface of the substrate, or
on a surface of the base and a surface of the substrate; and the
feeding electrodes of the plurality of feeding-radiating elements
are connected to matching points of the stub which are determined
based on the effective line length of the radiating electrodes.
2. An antenna apparatus according to claim 1, wherein a radiating
electrode without a feeding electrode is disposed on a surface of
the base so as to be adjacent to the radiating electrode of at
least one of the plurality of feeding-radiating elements.
3. An antenna apparatus according to claim 1, wherein the stub is a
short stub of which a portion far from the feeding point is coupled
to the ground.
4. An antenna apparatus according to claim 1, further comprising a
ground conductive layer disposed on the substrate, wherein the stub
is an open stub which is separated from the ground conductive layer
by a slit formed in the ground conductive layer.
5. An antenna apparatus according to claim 4, wherein a reactor is
connected between the stub and the ground conductive layer.
6. An antenna apparatus according to claim 5, wherein the reactor
includes a pattern electrode having a reactance component which is
disposed on the base.
7. An antenna apparatus according to claim 1, wherein the stub
includes a feeding land having a feeding point which is disposed on
the substrate, and a stub pattern which is disposed on the base and
which is connected to the feeding land.
8. An antenna apparatus according to claim 1, wherein the base is
made of a dielectric material.
9. An antenna apparatus according to claim 1, wherein the substrate
is made of an epoxy resin containing a glass fiber.
10. An antenna apparatus according to claim 1, further comprising a
ground conductive layer disposed on the substrate.
11. An antenna apparatus according to claim 4, wherein the slit
extends in a direction that is substantially perpendicular to an
edge of the substrate and is bent at a right angle and extending
substantially parallel to the substrate edge.
12. An antenna apparatus according to claim 1, wherein the
plurality of feeding-radiating elements include first and second
feeding-radiating elements, and the second feeding-radiating
element has an electrical length for excitation at a higher
frequency than that of the first feeding-radiating element.
13. An antenna apparatus according to claim 1, wherein a signal
power is supplied from the common feeding point positioned on the
substrate to the feeding electrodes according to different
reactance of the stub.
14. An antenna apparatus according to claim 1, wherein the
plurality of feeding-radiating elements include first and second
feeding-radiating elements, and the second feeding-radiating
element has a higher excitation frequency than that of the first
feeding-radiating element
15. An antenna apparatus according to claim 1, further comprising
at least one parasitic radiating element arranged on the base and
electromagnetically coupled with one of the feeding-radiating
elements to achieve dual resonance with the one of the
feeding-radiating elements.
16. An antenna apparatus according to claim 1, further comprising a
plurality of parasitic radiating elements arranged on the base and
electromagnetically coupled with respective ones of the
feeding-radiating elements to achieve dual resonance with the
respective ones of the feeding-radiating elements.
17. An antenna apparatus according to claim 4, wherein the open
stub defines a substantially U-shaped bar extending from the
substrate edge.
18. An antenna apparatus according to claim 5, wherein the reactor
includes one of a reactance pattern and a lumped element.
19. An antenna apparatus according to claim 5, wherein the reactor
is arranged to achieve impedance matching between each of the
feeding-radiating elements and the common feeding point.
20. An antenna apparatus according to claim 1, wherein the stub
includes a stub pattern disposed on a side surface of the base.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention generally relates to an antenna
apparatus, and more particularly, to an antenna apparatus having a
plurality of feeding-radiating elements.
[0003] 2. Description of the Related Art
[0004] In recent years, the number of cellular telephones using a
plurality of frequency bands has increased. Such cellular
telephones switch from one frequency band in which telephone
traffic concentration occurs to another frequency band to achieve
smooth telephone communication. The cellular telephones of this
type require an antenna which is excited in two frequency bands.
For example, U.S. Pat. No. 6,333,716 discloses an antenna for use
in GSM (Global System for Mobile Communications) cellular
telephones which is excited at frequencies in the 900 MHz and 1800
MHz bands.
[0005] This type of antenna includes a metallic pattern disposed on
a dielectric housing, and a slit formed in the metallic pattern to
form two feeding-radiating elements having different electrical
lengths, wherein a signal current fed from a common feeding point
causes one of the feeding-radiating elements to be excited at a
frequency in the 900 MHz band and causes the other
feeding-radiating element to be excited at a frequency in the 1800
MHz band.
[0006] However, typically, when a current is fed from a common
feeding point to a plurality of feeding-radiating elements, in a
frequency band allocated to each of the feeding-radiating elements,
sufficient radiating resistance may not be maintained for each
feeding-radiating element because each of the feeding-radiating
elements does not experience the optimum electrical length from the
feeding point to the feeding-radiating element, thereby making the
bandwidth for resonance narrower. Another problem arises in that
insufficient signal power supply resulting from no impedance
matching between each of the feeding-radiating elements and the
signal source causes insufficient gain of the feeding-radiating
elements, or causes variations in gain from one feeding-radiating
element to another.
SUMMARY OF THE INVENTION
[0007] In order to overcome the problems described above, preferred
embodiments of the present invention provide an antenna apparatus
having a plurality of feeding-radiating elements, wherein excellent
electrical matching is achieved for each of the feeding-radiating
elements.
[0008] According to a preferred embodiment of the present
invention, an antenna apparatus includes a dielectric base, a
plurality of feeding-radiating elements each including a feeding
electrode and a radiating electrode which are disposed on surfaces
of the base, and a substrate which fixedly supports the base,
wherein a common feeding point for feeding a current to the
plurality of feeding-radiating elements is disposed on the
substrate, a stub continuously expanding from the feeding point is
disposed on a surface of the substrate, or on a surface of the base
and a surface of the substrate, and the feeding electrodes of the
plurality of feeding-radiating elements are connected to matching
points of the stub which are determined based on the effective line
length of the radiating electrodes.
[0009] The feeding-radiating elements are excited at the resonance
frequency which depends upon the effective line length of the
radiating electrodes. Since the feeding electrode of each of the
feeding-radiating elements is connected to the matching point of
the stub which has the optimum stub length for each
feeding-radiating element, each feeding-radiating element can
achieve an excellent resonance property at the resonance frequency,
while the required bandwidth can be maintained in the frequency
band to which the resonance frequency belongs.
[0010] The stub length optimization for each of the
feeding-radiating elements allows the optimum impedance matching
between the feeding-radiating elements and the feeding point or the
signal source, thereby allowing the maximum power to be supplied
from the signal source to the feeding-radiating elements to
increase the gain of the feeding-radiating elements. The effective
line length L of a radiating electrode is expressed by
L=.lambda./4{square root}.di-elect cons., where .di-elect cons.
denotes the effective relative dielectric constant of a base, and
.lambda. denotes the wavelength of resonance frequency. As used
herein, "a surface of a base" indicates at least one surface of a
three-dimensionally shaped base. The stub may be a short stub or an
open stub, and is disposed on a surface of a substrate, or on a
surface of the substrate and a surface of a base.
[0011] Preferably, a radiating electrode without a feeding
electrode is arranged on a surface of the base so as to be adjacent
to the radiating electrode of at least one of the plurality of
feeding-radiating elements.
[0012] The radiating electrode without a feeding electrode defines
a parasitic radiating element. The parasitic radiating element is
electromagnetically coupled with a feeding-radiating element
adjacent thereto, and is thus energized to resonate at a frequency
in the same frequency band as that of the resonance frequency of
the adjacent feeding-radiating element. Accordingly, dual resonance
matching can be achieved between the resonance frequency of the
feeding-radiating element and the resonance frequency of the
parasitic radiating element, and the frequency bandwidth for the
dual resonance can thus be broader than the frequency bandwidth for
the resonance by the feeding-radiating element alone.
[0013] The stub may be a short stub of which a portion far from the
feeding point is coupled to the ground.
[0014] Therefore, the optimum reactance which is expressed by the
stub length using the ground potential as a reference for each of
the feeding-radiating elements can be applied to the
feeding-radiating elements. Then, the optimum resonance matching
can be achieved for each of the feeding-radiating elements. For
example, a longer stub length may be set for a feeding-radiating
element having a lower resonance frequency, while a shorter sub
length may be set for a feeding-radiating element having a higher
resonance frequency, thereby achieving the optimum impedance
matching between each of the feeding-radiating elements and the
feeding point.
[0015] The antenna apparatus further includes a ground conductive
layer provided on the substrate. The stub may be an open stub which
is separated from the ground conductive layer by a slit formed in
the ground conductive layer.
[0016] The reactance to be applied to each of the feeding-radiating
elements is provided based on a distance from a feeding point of
the open stub to the feeding electrode of each of the
feeding-radiating elements. Therefore, the feeding-radiating
elements can have an electrical length which achieves resonance
property optimization at a prescribed frequency band.
[0017] A reactor may be connected between the stub and the ground
conductive layer.
[0018] Since the stub is partially formed of a lumped element such
as a reactor, for example, an inductor or a capacitor, the
effective stub length can be changed by selecting the reactance of
the lumped element. When reactance is applied to an open stub, the
stub will be a short stub.
[0019] The reactor may include a pattern electrode having a
reactance component which is disposed on a surface of the base.
[0020] As a result, the stub length can be changed without using a
lumped element. The reactance of the pattern electrode can be
changed by changing the length, width, or configuration of the
pattern electrode. The pattern electrode can be provided on a
surface of the base together with a feeding electrode, and the
pattern formation can thus be readily performed.
[0021] The stub may include a feeding land having a feeding point
provided on the substrate, and a stub pattern which is disposed on
a surface of the base and which is connected to the feeding
land.
[0022] The feeding electrode of each of the feeding-radiating
elements may be integrally connected beforehand at the position of
a matching point of the stub pattern on the base. When one end of
the stub pattern is connected to the feeding land, final matching
between each of the feeding-radiating elements and the feeding
point or supply source is achieved. The stub pattern may be a short
stub by coupling to the ground the end of the stub pattern opposite
to the end which is connected to the feeding land. Alternatively,
the stub pattern may be an open stub by making the opposing end
open. The optimum stub length from the matching point to the
feeding electrode of each of the feeding-radiating elements can be
changed by changing the length and width of the stub pattern.
[0023] Other features, elements, characteristics and advantages of
the present invention will become more apparent from the following
detailed description of preferred embodiments thereof with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a perspective view of an antenna apparatus
according to a first preferred embodiment of the present
invention;
[0025] FIG. 2 is an exploded perspective view of the antenna
apparatus shown in FIG. 1;
[0026] FIG. 3 is a perspective view of an antenna apparatus
according to a second preferred embodiment of the present
invention;
[0027] FIG. 4 is a perspective view of an antenna apparatus
according to a third preferred embodiment of the present
invention;
[0028] FIG. 5 is a perspective view of an antenna apparatus
according to the third preferred embodiment of the present
invention;
[0029] FIG. 6 is a perspective view of an antenna apparatus
according to the third preferred embodiment of the present
invention; and
[0030] FIG. 7 is a perspective view of an antenna apparatus
according to a fourth preferred embodiment of the present
invention.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0031] The present invention is hereinafter described with respect
to its specific preferred embodiments, taken in conjunction with
the drawings. FIG. 1 shows an antenna apparatus according to a
first preferred embodiment of the present invention.
[0032] In FIG. 1, a substrate 1 is a mounting substrate made of,
for example, epoxy resin containing a glass fiber. A ground
conductive layer 2 which is a conductor made of copper or other
suitable material is disposed on one surface of the substrate 1. A
slit 3 having a substantially L-shaped configuration starting from
a substrate edge 1a is formed in the ground conductive layer 2.
Specifically, the slit 3 first extends in a direction that is
substantially perpendicular to the substrate edge 1a, and is then
bent at a right angle, extending substantially parallel to the
substrate edge 1a. The slit 3 produces a tongue-like short stub 4
extending along the substrate edge 1a with an equal width. The root
portion of the short stub 4 joins with the ground conductive layer
2, and a feeding point 5 connected to a signal source (not shown)
is positioned on the tip 4a of the short stub 4.
[0033] A substantially rectangular-block base 6, which is
preferably made of a dielectric material such as a ceramic material
or a plastic material, has a first feeding-radiating element 7 and
a second feeding-radiating element 8 disposed thereon. The first
feeding-radiating element 7 includes a first strip feeding
electrode 9 which extends in the vertical direction across a first
side surface 6b of the base 6, a first radiating electrode 11 which
extends straight from the top end of the first feeding electrode 9
on the principal surface 6a of the base 6 and which turns around
near a side surface 6d facing the first side surface 6b along a
second side surface 6c, and a capacitive electrode 13 which extends
downward from the turnaround portion of the first radiating
electrode 11 on the second side surface 6c of the base 6. The first
feeding-radiating element 7 has an electrical length for excitation
at a frequency of a predetermined frequency band, for example, the
900 MHz band.
[0034] The second radiating element 8 includes a second strip
feeding electrode 10 which extends substantially parallel to the
first feeding electrode 9 on the first side surface 6b of the base
6, and a second radiating electrode 12 which expands to the left
from the top end of the second feeding electrode 9 on the principal
surface 6a of the base 6. Accordingly, the second feeding-radiating
element 8 has an electrical length for excitation at a higher
frequency than the resonance frequency, for example, at a frequency
of the 1800 MHz band.
[0035] The base 6 including the first feeding-radiating element 7
and the second feeding-radiating element 8 is fixed preferably by
soldering to the ground conductive layer 2 of the substrate 1 using
a fixed electrode (not shown) formed on the bottom of the base 6.
The bottom end of the first feeding electrode 9 of the first
feeding-radiating element 7 and the bottom end of the second
feeding electrode 10 of the second feeding-radiating element 8 are
soldered to different portions of the short stub 4. Therefore, a
signal power is supplied from the feeding point 5 positioned on the
substrate 1 to the first and second feeding electrodes 9 and 10
according to different reactance of the short stub 4.
[0036] More specifically, as shown in FIG. 2, since the electrical
length of the first feeding-radiating element 7 is different from
the electrical length of the second feeding-radiating element 8,
the impedance matching to the feeding point 5, namely, the signal
source, is separately performed for the first feeding-radiating
element 7 and the second feeding-radiating element 8. In the
following description, for simplification of illustration, the
widths of the first and second feeding electrodes 9 and 10 are
represented by feeding nodes 9a and 10a, respectively.
[0037] The reactance of the short stub 4 is given based on the stub
length. Specifically, since the short stub 4 is separated from the
ground conductive layer 2 by the slit 3, the reactance for the
first feeding-radiating element 7 is given based on length (stub
length) L1 from a ground point 2a at the leading end portion of the
slit 3 to a first matching point 4b. Likewise, the reactance for
the second feeding-radiating element 8 is given based on stub
length L2 from the ground point 2a to a second matching point
4c.
[0038] The feeding node 9a of the first feeding-radiating element 7
is connected to the first matching point 4b of the short stub 4,
and the reactance given based on the stub length L1 is applied to
the first feeding-radiating element 7. This provides the optimum
impedance matching between the first feeding-radiating element 7
and the feeding point 5, resulting in a satisfactory resonance
property at the first feeding-radiating element 7.
[0039] The feeding node 10a of the second feeding-radiating element
8 is connected to the second matching point 4c of the short stub 4,
and the reactance given based on the stub length L2 is applied to
the second feeding-radiating element 8. Since the second
feeding-radiating element 8 is excited at a higher frequency than
that of the feeding-radiating element 7, the second
feeding-radiating element 8 requires lower reactance for the
optimum impedance matching to the feeding point 5 than that of the
first feeding-radiating element 7. Thus, the stub length L2 is
shorter than the stub length L1, i.e., L1>L2.
[0040] Accordingly, the first and second feeding electrodes 9 and
10 of the first and second feeding-radiating elements 7 and 8 are
coupled to the optimum matching points 4b and 4c of the short stub
4, respectively, thereby providing a satisfactory resonance
property for each of the first feeding-radiating element 7 and the
second feeding-radiating element 8. The optimum impedance matching
allows the maximum power to be supplied to the first and second
feeding-radiating elements 7 and 8, so that the gain of the first
and second feeding-radiating elements 7 and 8 is high.
[0041] The stub length optimization for each of the first and
second feeding-radiating elements 7 and 8 allows sufficient
radiating resistance to be maintained for resonance in each of the
first and second feeding-radiating elements 7 and 8. Therefore, a
sufficient bandwidth can be maintained in the frequency bands for
the individual resonance by the first feeding-radiating element 7
and the second feeding-radiating element 8.
[0042] An antenna apparatus according to a second preferred
embodiment of the present invention is now described with reference
to FIG. 3. The feature of the second preferred embodiment is that
dual resonance is achieved by the addition of a parasitic radiating
element. The same reference numerals are given to the same
components as those in the first preferred embodiment shown in FIG.
1, and duplicative description thereof is omitted.
[0043] In FIG. 3, a first feeding-radiating element 15 and a second
feeding-radiating element 16 are disposed on the principal surface
6a of the base 6. The first feeding-radiating element 15 includes a
strip radiating electrode 17 extending from the top end of the
feeding electrode 9 to the side surface 6d, and the strip radiating
electrode 17 is then connected to a capacitive electrode 19. The
second feeding-radiating element 16 includes a strip radiating
electrode 18 extending from the top end of the feeding electrode 10
on the principal surface 6a substantially parallel to the radiating
electrode 17. The second feeding-radiating element 16 is excited at
a higher frequency than that of the first feeding-radiating element
15.
[0044] A first parasitic radiating element 20 is adjacent to the
first feeding-radiating element 15. A ground electrode 22 of the
first parasitic radiating element 20 is disposed on the side
surface 6b on which the feeding electrodes 9 and 10 are provided,
and the bottom end of the ground electrode 22 is connected to the
ground conductive layer 2. The first parasitic radiating element 20
extends from the top end of the ground electrode 22 on the
principal surface 6a in parallel to the radiating electrode 17. The
first parasitic radiating element 20 is turned around toward the
second side surface 6c before reaching the side surface 6d, and is
then connected to a capacitive electrode 26 disposed on the second
side surface 6c.
[0045] The first parasitic radiating element 20 is
electromagnetically coupled with the first feeding-radiating
element 15 to receive a supply of excitation power, and dual
resonance is achieved at the same frequency band.
[0046] Like the first parasitic radiating element 20, a second
parasitic radiating element 21 includes a ground electrode 23 and a
radiating electrode 25 disposed on the surfaces of the base 6, and
is adjacent to the second feeding-radiating element 16. The
radiating electrode 25 of the second parasitic radiating element 21
is electromagnetically coupled with the second feeding-radiating
element 16 to achieve dual resonance at the same frequency with the
second feeding-radiating element 16 having an electrical length
adjusted according to the reactance of the stub 4, resulting in a
broader bandwidth.
[0047] An antenna apparatus according to a third preferred
embodiment of the present invention is now described with reference
of FIG. 4. The feature of the third preferred embodiment is that an
open stub is provided. The same reference numerals are assigned to
the same elements as those in the first preferred embodiment shown
in FIG. 1, and a duplicative description thereof is omitted.
[0048] In FIG. 4, a portion of the ground conductive layer 2 of the
substrate 1 is separated by a slit 28, where an open stub 29 is
provided. The slit 28 is formed in the ground conductive layer 2 to
form a substantially U-shaped bar extending from the substrate edge
1a. The separated portion of the ground conductive layer 2 defines
the substantially rectangular stub 29 extending along the substrate
edge 1a.
[0049] The feeding point 5 is positioned at the end of the stub 29
near the first feeding-radiating element 7. The effective stub
length from the feeding point 5 to the feeding electrode 10 of the
second feeding-radiating element 8 is longer than the effective
stub length from the feeding point 5 to the feeding electrode 9.
This allows reactance that is different from that of the first
feeding-radiating element 7 to be applied to the second
feeding-radiating element 8. Therefore, the impedance matching to
the feeding point 5 or the signal source is separately performed
for the first and second feeding-radiating elements 7 and 8. It is
noted that the feeding point 5 may be placed at a different
position to achieve impedance matching to the first
feeding-radiating element 7 and the second feeding-radiating
element 8.
[0050] As shown in FIG. 5, the open stub 29 in the third preferred
embodiment shown in FIG. 4 may be changed to a short stub by
connecting a reactor 30 over the slit 28 between the open stub 29
and the ground conductive layer 2. The reactor 30 may be
implemented as an inductor such as a chip inductor, or a capacitor
such as a chip capacitor may be used depending upon the matching
condition.
[0051] With this structure, the effective stub lengths from the
ground potential to the feeding electrodes 9 and 10 of the first
and second feeding-radiating elements 7 and 8 may be changed by
selecting the reactance of the reactor 30. That is, the effective
stub length from the ground potential of the ground conductive
layer 2 to the feeding electrode 9 is determined based on the
reactance of the reactor 30 to achieve impedance matching between
the first feeding-radiating element 7 and the feeding point 5 or
the signal source. Likewise, the effective stub length from the
ground potential to the feeding electrode 10 is determined based on
the reactance of the reactor 30 to achieve impedance matching
between the second feeding-radiating element 8 and the feeding
point 5.
[0052] As shown in FIG. 6, the reactor 30 which bridges between the
open stub 29 and the ground conductive layer 2 may be constructed
by a reactance pattern 31 disposed on the first side surface 6b of
the base 6, rather than a lumped element. The reactance pattern 31
is a meandering pattern electrode having an inductance component.
One end of the reactance pattern 31 is connected to the ground
conductive layer 2, and the other end of the reactance pattern 31
is connected to the open stub 29. The inductance of the reactance
pattern 31 may be adjusted by trimming the reactance pattern
31.
[0053] An antenna apparatus according to a fourth preferred
embodiment of the present invention is now described with reference
to FIG. 7. The feature of the fourth preferred embodiment is that a
stub pattern is disposed on a side surface of a base. The same
reference numerals are assigned to the same elements as those in
the first preferred embodiment shown in FIG. 1, and a duplicative
description thereof is omitted.
[0054] In FIG. 7, the feeding point 5 is positioned on a feeding
land 32 which is separated from the ground conductive layer 2 by a
slit 34. A stub pattern 33 is disposed on the first side surface 6b
of the base 6 so as to be aligned with the feeding electrodes 9 and
10 and to bridge over the slit 34. A feeding end 33a of the stub
pattern 33 is connected to the feeding land 32, and is formed by
extending the feeding electrode 9 of the feeding-radiating element
7 to the bottom end of the base 6. A ground end 33b of the stub
pattern 33 is connected to the ground conductive layer 2 of the
substrate 1. This enables the stub pattern 33 and the feeding land
34 to function as a short stub.
[0055] In the stub pattern 33, the feeding electrodes 9 and 10 of
the feeding-radiating elements 7 and 8 are integrally arranged, and
the node therebetween is set at the optimum matching point which is
determined according to the stub length originating from the ground
end 33b of the stub pattern 33. The effective stub length can be
changed by changing the length and width of the stub pattern 33.
The effective stub length can also be changed by changing the
position at which the feeding end 33a of the stub pattern 33 is
connected to the feeding land 32, namely, a distance from the
feeding point 5 to the feeding end 33a.
[0056] As described above, in an antenna apparatus according to
preferred embodiments of the present invention, a feeding electrode
of each of a plurality of feeding-radiating elements is connected
to a matching point of a stub with a feeding point, thereby
achieving the optimum matching at a frequency allocated to each of
the feeding-radiating elements. Thus, the antenna apparatus
achieves a very high gain and a sufficient frequency bandwidth.
[0057] Furthermore, a parasitic element is adjacent to at least one
feeding-radiating element to achieve dual resonance, and the
frequency bandwidth to which the resonance frequency for the dual
resonance belongs can thus be broader than the frequency bandwidth
for the resonance by the feeding-radiating element alone.
[0058] The stub may be a short stub of which a portion far from the
feeding point is coupled to the ground, and the optimum matching
for each feeding-radiating element can thus be achieved using the
stub length from the ground potential.
[0059] The stub may be an open stub which is separated from a
ground conductive layer provided on the substrate by a slit formed
in the ground conductive layer, and the stub can thus be readily
formed. The matching points required for the respective
feeding-radiating elements can also be determined.
[0060] Furthermore, a reactor may be connected between the open
stub and the ground conductive layer, thereby achieving the desired
impedance matching between each of the feeding-radiating elements
and the feeding point by selecting the reactance of that lumped
element.
[0061] Furthermore, a reactance pattern may be located on a surface
of a base having feeding-radiating elements disposed thereon,
thereby achieving impedance matching between each of the
feeding-radiating elements and the feeding point based on the
reactance without use of a lumped element.
[0062] Furthermore, a stub may include a feeding land provided on
the substrate, and a stub pattern disposed on the base, thereby
achieving simultaneous formation of the stub pattern and feeding
electrodes in consideration of a difference between the matching to
one feeding-radiating element and the matching to another
feeding-radiating element.
[0063] While the present invention has been described with
reference to what are at present considered to be preferred
embodiments, it is to be understood that various changes and
modifications may be made thereto without departing from the
invention in its broader aspects and therefore, it is intended that
the appended claims cover all such changes and modifications that
fall within the true spirit and scope of the invention.
* * * * *